#1 Largest Private Schools in Boulder County, CO
Boulder Country Day School
Independent school · Grades Pre-K–8
281 students
Boulder, CO
B+Overall grade281 students6 students per teacher
2026 lists
Largest Private Schools in Boulder County, CO
The private schools in Boulder County, CO with the most students. Top 22 of 22 schools.
#2 Largest Private Schools in Boulder County, CO
Shining Mtn. Waldorf High School
Independent school · Grades Pre-K–12
188 students
Boulder, CO
AOverall grade188 students5 students per teacher
#3 Largest Private Schools in Boulder County, CO
St. John the Baptist Catholic School
Diocesan school · Grades Pre-K–8
185 students
Longmont, CO
A+Overall grade185 students10 students per teacher
#4 Largest Private Schools in Boulder County, CO
Shining Mountain Waldorf School
Independent school · Grades Pre-K–12
170 students
Boulder, CO
B-Overall grade170 students10 students per teacher
#5 Largest Private Schools in Boulder County, CO
Sacred Heart of Jesus School
Parish school · Grades Pre-K–8
169 students
Boulder, CO
A+Overall grade169 students6 students per teacher
#6 Largest Private Schools in Boulder County, CO
Friends School
Independent school · Grades Pre-K–8
134 students
Boulder, CO
B-Overall grade134 students
#7 Largest Private Schools in Boulder County, CO
Watershed School
Independent school · Grades 6–12
114 students
Boulder, CO
BOverall grade114 students7 students per teacher
#8 Largest Private Schools in Boulder County, CO
Rocky Mountain Christian Academy
Christian school (nondenominational) · Grades Pre-K–8
98 students
Niwot, CO
A-Overall grade98 students7 students per teacher
#9 Largest Private Schools in Boulder County, CO
Boulder Valley Waldorf School
Independent school · Grades Pre-K–8
95 students
Niwot, CO
A-Overall grade95 students5 students per teacher
#10 Largest Private Schools in Boulder County, CO
St. Louis Catholic School
Parish school · Grades Pre-K–8
93 students
Louisville, CO
A+Overall grade93 students8 students per teacher
#11 Largest Private Schools in Boulder County, CO
Bixby School
Independent school · Grades Pre-K–5
93 students
Boulder, CO
A+Overall grade93 students4 students per teacher
#12 Largest Private Schools in Boulder County, CO
Hillside School
Special education school · Grades 1–9
75 students
Longmont, CO
B+Overall grade75 students6 students per teacher
#13 Largest Private Schools in Boulder County, CO
Jarrow Montessori School
Montessori school · Grades Pre-K–6
70 students
Boulder, CO
BOverall grade70 students8 students per teacher
#14 Largest Private Schools in Boulder County, CO
Mapleton Montessori School
Montessori school · Ungraded
48 students
Boulder, CO
A-Overall grade48 students6 students per teacher
#15 Largest Private Schools in Boulder County, CO
Longmont Christian School
Christian school (nondenominational) · Grades Pre-K–8
47 students
Longmont, CO
A+Overall grade47 students4 students per teacher
#16 Largest Private Schools in Boulder County, CO
Mountain Shadows Montessori School
Montessori school · Grades Pre-K–4
44 students
Boulder, CO
A-Overall grade44 students6 students per teacher
#17 Largest Private Schools in Boulder County, CO
Autana Montessori School
Montessori school · Grades Pre-K–K
42 students
Lafayette, CO
B+Overall grade42 students7 students per teacher
#18 Largest Private Schools in Boulder County, CO
Tara Performing Arts High School
Independent school · Grades 9–12
39 students
Boulder, CO
AOverall grade39 students4 students per teacher
#19 Largest Private Schools in Boulder County, CO
Boulder Sudbury School
Religious school · Ungraded
37 students
Longmont, CO
37 students11 students per teacher
#20 Largest Private Schools in Boulder County, CO
Crossroads School
Christian school (nondenominational) · Grades 7–12
30 students
Longmont, CO
AOverall grade30 students7 students per teacher
#21 Largest Private Schools in Boulder County, CO
Fusion Academy, Boulder County
Independent school · Grades 6–12
29 students
Louisville, CO
A-Overall grade29 students3 students per teacher
#22 Largest Private Schools in Boulder County, CO
Temple Grandin School
Special education school · Grades 6–12
22 students
Boulder, CO
AOverall grade22 students3 students per teacher
From official public records, updated October 2026.